Artificial hollow thread manufacturing process



' Patented Nov. 10, 1931 UNITED, STATES PATE NT OFFICE j m BASEL, A CORPORA- TION F SWITZERLAND ARTIFICIAL HOLLOW THREAD MANUFACTURING PROCESS- No brewing. Application filed. April 27, 1928, Serial No.'273,426, and in'Germany April 30,1927,

Persons skilled in the art are aware of the prior artificial hollow thread manufacturing rocesses or methods patents Brandenberger 0. 1,394,270, Rousset No; 1,487,807 and T Brandenberger No. 1,544,631) including those wherein viscose havinga carbonate dis solved therein is spun in an acid bath.-

The spaces or voids produced in the filaments may be formed of 'adjoined bubbles separated by cross partitions. Such threads generally maintain their hollow spaces on account of the rigidity imparted thereto by theircross-partitions.

In other instances, the hollow threads have only a few partitions, or none at all, whereby, and particularly in the case of fine filaments, the outer walls will close in or collapse, somewhat after the manner of a collapsed rubber tube. These threads generally have less covering power than the cross-partitioned ones.

This invention contemplates the manufacturing of hollow threads endowed with a higher covering power, even where the spaces are partitionless.

The process or method constituting the invention is characterized by the fact that acid coagulating baths containing a high propor-' tion of zinc sulphate (practically over 6%) are used. a

In the coagulating bath containing zinc sulphate hitherto used in artificial silk manufacturing practice, the zinc sulphate proportion is aboutl% and, according to DRP Patent No. 260,479, should not exceed 5 in order to avoid noxiousness. On the other hand, English patent discloses baths for hollow thread manufacturing containing zinc sulphate up to 4% and 5%.

Said patents do not cover the use of a relatively large proportion of zinc sulphate in coagulating baths nor do they recognize the remarkable effect arising therefrom as to the covering power of threads so obtained.

The influence of high zinc sulphate proportions on coagulation is such that when the bath contains nothing but sulphuric acid and sulphate of zinc, the latter in a proportion, there is obtained a hollow thread which-weight equal-bulks far more than a any obtained by hitherto known methods.

In addition to sulphuric acid and zinc sulphate, the coagulating bath may also contain sulphate of soda or other coagulating salts, or such products as glucose, which have been found advantageous in the artificial silk industry,

Practical 'ewampZe.-In a normal viscose containing: cellulose 7%, and alkali 6, 5%, &% of carbonate of soda solution is then allowed to ripen or mature until it possesses a salt point of 10 (an explanation of salt point is given in French Patent No. 577,369 dated August 13th, 1923), at which time it is spun in a coagulating bath composed as follows Grams per liter Sulphuric acid 120 Zinc sulphate 220 Sulphate of soda 40 under the conditions required to obtain a unit strand of- 3, 7 dwt.

The thread is then finished according to the usual artificial silk treatment. 7 Having now particularly ascertained and described the nature of my said invention as well as the manner in which the same is to be performed, I declare that what I claim is:

1. In a process of producing hollow artificial silk threads the step which comprises spinning the viscose solution in an acid coagulating bath containing zinc sulphate inexcessof6%. V

2. In a method of producing hollow artificial silk threads the step which comprises spinning the viscose solution in an acid coagulating bath containing 6% to 30% of zinc sulphate.

3. In a process of producing hollow artificial silk threads the step which comprises spinning the viscose solution in a coagulating bath comprising 120 grams per liter of sulphuric acid, 220'grams per liter of zinc sulphate andO grams per liter of sodium sulphate. a p V In testimony whereofI affix my signature.

' RENE PICARD.

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